1. Field of the Invention
The present invention relates to a filtration apparatus for filtering and separating solids from liquids comprising at least one liquid-permeable, continuously or intermittently drivable filter belt, an intake for charging the liquid/solid mixture to be filtered onto the filter belt in a charging zone and a belt cleaner for removing the solids deposited at the filter belt from a belt section conveyed out of the charging zone in an expulsion zone.
2. Description of the Related Art
A pelletizing apparatus is known from the document DE 101 54 134 A1 whose process liquid is conducted through a particle filter in the form of a liquid coolant in a circuit to filter and separate from the process liquid contaminants which enter into the process liquid during pelletizing or granulation. A filter belt running around continuously in the manner of a conveyor belt is provided as a particle filter in this respect, with the contaminated process liquid to be filtered being charged onto said filter belt so that the liquid runs through the upper run and lower run of the filter belt and particles are collected on the filter belt. The contaminants collected on the belt are transported away and are removed continuously from the belt using a scraper in an expulsion zone.
The use of continuously or intermittently drivable filter belts for filtering contaminated liquids is in particular advantageous in industrial plants in which process liquid is conducted in a circuit since the plant does not need to be stopped to clean the filter. The solids deposited on the filter belt in the charging zone are conducted out of the charging zone by the movement of the filter belt so that they can be removed from the filter belt in an expulsion zone which is disposed outside said charging zone. At the same time, a fresh or cleaned filter belt section is newly moved into the charging zone by the movement of the filter belt so that a fresh, functional filter belt section always carries out the filtration there.
The previously known filtration apparatus of this category are, however, needful of improvement in a number of respects. In this respect, one problem relates to the cleaning and servicing of the filter belt. The solids collecting both at the upper run and at the lower run of the filter belt in the apparatus in accordance with DE 101 54 134 A1 cannot be removed easily before the respective run of the filter belt is conducted around the deflection roller disposed in the interior of the filtration apparatus since a filter belt section is not first conducted into the expulsion zone via the scraper arranged there before the corresponding filter belt section in the interior of the filtration apparatus changes from the lower run to the upper run or—depending on the direction of rotation—from the upper run to the lower run. Not only the solids deposited at the filter belt are hereby conducted around the deflection roller disposed in the interior of the filtration apparatus, which results in solidification, but also in wear at the belt and deflection roller, but also the filter belt section covered with solids in the upper run is used for filtration again without previously having been cleaned.
Furthermore, problems can result in the cleaning off of the filter belt in the expulsion zone which require separate cleaning measures and thus a standstill of the filtration apparatus. On the one hand, this can be due to the fact that deposits solidified at the filter band cannot be completely scraped off and accumulate more and more on a repeated running around of the filter belt so that the filter belt clogs. On the other hand, the solids removed from the filter belt can accumulate at the scraper so that an accumulation can result there which requires a maintenance standstill of the filtration apparatus.
On such maintenance standstills, the handling of such filtration apparatus having a revolving filter belt has previously been much more complex than with stationary edge split filters. If, for example, the filter belt has to be completely replaced, the removal of the filtration apparatus is considerably more complex since the deflection roller in the interior of the filtration apparatus also has to be removed, at least for the installation of a new continuously running filter belt, if the ends of a non-continuous filter belt should not be connected to one another subsequently, i.e. after threading in said non-continuous filter belt.
Starting from this, it is the underlying object of the present invention to provide an improved filtration apparatus of the initially named type which avoids disadvantages of the prior art and further develops the latter in an advantageous manner. Longer operating cycles with fewer and shorter maintenance downtimes should preferably be achieved without impairing the filtration efficiency. Furthermore, an easier replaceability of the filter belt should preferably be made possible to be able to carry out adaptations of the filtration apparatus to different process liquids or to solids contained therein.